Forex market is not centralized, there is no way to see the real volume. The volume your MT4 shows is not anywhere near the correct number.

I use ECN myself and see the level II style market depth and that still is not the true volume (and I know that).

The only way to get some visibility is to track volumes from currency futures contracts (which are centralized) but that's quite a different story..

In other words, it's not worth using volume indicators in forex.